This invention relates to reducing chatter which occurs e.g. during cold-rolling of steel sheets/plates. Under unfavourable operating conditions, periodic oscillations appear in addition to base oscillations and they grow exponentially. The rolled product thereby suffers from a reduction in quality. This leads to rejects and also to damage to the rolling mill. Also with low chatter instability, so called thickness and/or surface waves occur. The same chatter phenomena also occur in the manufacture of many products other than steel including paper; tapes or wires.
When exceeding a certain oscillation amplitude, a rolling parameter is changedxe2x80x94usually the rolling speed is reducedxe2x80x94in order to get out of the critical operation range. Such a process is not satisfactory, since it does not eliminate the primary cause.
In GB-A-1036922 it is suggested to avoid roll oscillations by using a roll shaped oscillation absorber, which has a thin, hard outer layer (e.g. steel) and thereunder a softer, oscillation damping layer (e.g. rubber), the rest of the roll body being a solid body. The soft damping layer provides a decoupling of oscillations. However, the damping achieved with this arrangement is low. In U.S. Pat. No. 3,111,894 it is described how the oscillation behaviour of a rolling mill is influenced by the contact pressure of rolls, i.e. the eigenfrequencies are shifted. Moreover, a roll is described that has an outer rubber layer and should thereby be able to damp the oscillations of rolls that are coupled to it. As already mentioned above, a rubber layer primarily provides an oscillation decoupling. The damping effect of such a measure is low.
The problem underlying the invention is to introduce, a priori, an inhibitor of self-excited oscillations in rolling processes. This problem is solved by incorporating wave guides into a roll. The location is determined by the motions within the mode shapes that tend to feed back resonance oscillations. Technical executions of the wave guides are oscillation absorbers, as e.g. described in xe2x80x9cVDI-Richtlinie 2737, Blatt 1. (1980)xe2x80x9d [Guideline No2737 of the Association of German Engineers, sheet 1. (1980)], and resonance dampers. Oscillation absorbers have a spectrally adjustable resistance. Wave guides that are effective for several transitional and rotational degrees of freedom are of advantage. Suitable for this invention are oscillation absorbers of a layered construction type, as known per se from DE-A-2412672 and DE-A-3113268 the disclosures of which are herein incorporated by reference. Resonance dampers, on the other hand, are only effective at their resonance frequency and they can only be used where the chatter frequency is exactly known and constant. By incorporating the wave guide into a roll, the resistance of the wave guide can be very closely and rigidly coupled to the locations in which the rolling energy is transformed into work of deformation, to reduce instability by introducing rolling forces and rolling moments with a degressive force characteristic.